Vanilla bean drying and curing

ABSTRACT

Green vanilla beans are chopped into approximately one-half inch lengths, cured for about 70-78 hours in perforated trays within a closed tank maintained at about 140* F., exudate being returned to the beans; dried in a rotary forced air, hot water jacketed drier at about 140* F. until reduced to about 35-40 percent moisture by weight, transferred to a conditioner and dried more slowly with air at room temperature and humidity until reduced to about 20-25 percent moisture content by weight.

United States Patent Karas et al.

[54] VANILLA BEAN DRYING AND CURING [72] Inventors: Albert J. Karas;Richard L. Hall; William H. Stahl, all of Baltimore, Md.

[73] Assignee: McCormick & Company, Incorporated,

Baltimore, Md.

[22] Filed: Mar. 27, 1968 [21] App]. No.: 716,499

[52] U.S.C1. ..99/140R [51] Int. Cl. ..A23l 1/22 [58] Field of Search..99/140 [56] References Cited UNITED STATES PATENTS 2,621,127 12/1952Towt .99/140 51 May 16, 1972 3,352,690 11/1967 Kaul ..99/140 PrimaryExaminerJoseph Scovronek Assistant Examiner-Warren BoveeAtt0rneyCushman, Darby & Cushman ABSTRACT Green vanilla beans arechopped into approximately one-half inch lengths, cured for about 70-78hours in perforated trays within a closed tank maintained at about 140F., exudate being returned to the beans; dried in a rotary forced air,hot water jacketed drier at about 140 F. until reduced to about 35-40percent moisture by weight, transferred to a conditioner and dried moreslowly with air at room temperature and humidity until reduced to about20-25 percent moisture content by weight.

6 Claims, 2 Drawing Figures BACKGROUND AND SUMMARY OF THE INVENTIONVanilla beans require about 6 months to become fully grown or developedon the vine. During this growing stage the beans are green in color. Atthe end of the growing stage, while still green in color, the beans areharvested and sometimes referred to as blossom-end yellow or mature.After harvesting, it is conventional to cure the beans. During thecuring cycle, regardless of the method used, the beans turn from greento brown. Thus a green" vanilla bean is a harvested, mature" bean whichhas not yet been cured.

After curing and drying, vanilla beans may be ground and the particulatematerial used as food flavoring, for instance in vanilla flavored icecream or vanilla flavored granulated sugar; or the dried and cured beansmay be ground and vanillin and other flavoring constituents extractedthere-from in conventional liquid extraction processes.

The present invention has no particular concern with the growing orpicking of the beans or with their use in the preparation of an extract.The present invention is concerned with providing consistent highquality dried and cured vanilla bean of improved vanillin content.

The commonly assigned, earlier U.S. Pat. No. 2,621,127 of Towt containsat column 1, lines 14-36, a good discussion of two variants ofconventional curing processes and goes on to disclose a more rapidprocess wherein the green beans are pulped, heated in pressurized airwhile being agitated and dried to desired moisture content, the wholeprocess requiring much less time than the then conventional processes.By this reference the entire disclosure of the Towt patent is intendedto be incorporated herein.

While the Towt process represented a vast saving of time, effort andequipment hold up over the then conventional processes and provided auniform output, it has been determined that the amount and quality ofvanillin and other desired flavoring materials obtainable from vanillabean puree dried and cured according to the Towt process are about thesame as, or lower than, the amount and quality obtainable fromconventionally cured beans. In addition, the puree has been found to bedifficult to handle, doesnt look like vanilla beans, is susceptible ofhard-to-detect adulteration and portions of the puree may be lost duringprocessing. Thus this prior art process has disadvantages as well asadvantages, which fact has led to research directed to providing aprocess for drying and curing vanilla beans more quickly than oldconventional methods, while preserving the beans in an easily handledform, recognizable as vanilla beans, and improving the quality andquantity of vanillin and other desired flavoring materials recoverablefrom the dried and cured beans.

In carrying out the preferred embodiment of the present invention, thegreen vanilla beans are chopped into approximately one-half inchlengths, cured for about 70 78 hours in perforated trays within a closedtank maintained at about 140 F., exudate being returned to the beans;dried in a rotary forced air, hot water jacketed drier at about 140 F.until reduced to about 35 40 percent moisture by weight, trans ferred toa conditioner and dried more slowly with air at room temperature andhumidity until reduced to about 20 25 percent moisture content byweight.

The principles of the invention will be further hereinafter discussedwith reference to the drawing wherein a preferred embodiment is shown.The specifics illustrated in the drawing are intended to exemplify,rather than limit, aspects of the invention as defined in the claims.

IN THE DRAWING:

FIG. 1 is a schematic view of the steps of the process according to thepreferred embodiment of the invention, also illustrating certainapparatus elements in schematic form; and

FIG. 2 is a graphic view of the drying process comparing the processaccording to the preferred embodiment of the invention with anotheralternative.

DESCRIPTION OF THE PREFERRED EMBODIMENT The vanilla beans are inspectedfor quality at the factory door, and if accepted are weighed in. It isessential that all beans are mature. (Immature beans, similarlyprocessed separately, have given very inferior results, particularly inkeeping qualities.) Beans which appear overripe, that is, split andblackened, may be used and appear to have no deleterious effect on thefinished product. Beans left untreated until they have partially cured,turning brown as a result of not being processed within one or two days,have been treated separately. The latter showed a good vanillin contentand may be conventionally extracted to produce acceptable vanillaextract having no off notes.

When a batch, for instance, 1,050 pounds of green beans, has beencollected, the beans are conveyed to a bean cutter. lf insufficient cropis coming in to make up a batch all at once, then manufacture takesplace weekly. Keeping the green vanilla beans for this length of timebefore curing appears to have no adverse effect on the quality andquantity of output from the process of the invention.

The bean cutter chops the beans into lengths of one-half inch anddelivers them directly to a curing tray. On the delivery side of thecutter the beans pass over a perforated sheet which allows some of thesplit pieces and ends to fall through. These are rejected. If cured thesplit pieces and ends have a very low vanillin content. In any case theymake up by weight less than 0.25 percent of the vanilla. Apart from theabove-mentioned perforated sheet which is galvanized, all surfaces withwhich the vanilla comes in contact until it is packed are of stainlesssteel.

The curing trays in the example under discussion are 6% inches deep and36 /2 inches in diameter, the bottoms being perforated bythree-sixteenths inch holes at 12 to the square inch. Each try holdsabout 150 pounds of cut green beans. The trays are stacked seven deep ina frame which is then lifted and carried by overhead runway and droppedinto the curing tanks. The curing tanks are lined with stainless steeland are constructed of three-sixteenths inch mild steel plate. Each tankhas a waterjacket which is maintained at 140 F. There is a drain at thebottom of each tank, beneath which is suspended a stainless steel cup tocatch any liquid from the beans. In fact, very little exudes duringcuring, perhaps onehalf pint, but this has a strong odor of vanillin andis returned to the beans.

The tanks are closed during the curing process which typically lastsabout 72 hours. The exact time does not appear very critical, as inpractice it has ranged between 70 and 78 hours with no observable effecton the end product. At the end ofcuring the bean pieces have assumed avery deep brown color and are ready for transfer to the drier. This maybe done immediately but if they are left alone for, for instance, abouttwo days it appears to have no deleterious effect.

In developing the process according to the present invention, attemptswere made to dry the cured bean pieces to 20 25 percent moisture contentusing a rotary drier having a water jacket which is maintained at 140 F.and a heat exchanger and fan by means of which air at 140 F. is blownthrough the drier. The temperature of the curing tanks and rotary drierwater jackets, related as preferably being 140 F may range between about120 and 160 F. without producing deleterious results.

The great disadvantage of this was that it was very liable to overdrythe beans, as the drying rate at this point is surprisingly rapid, asnoted later herein, and the process difficult to control with thedesired precision. Due to the fact that the rotary drier is heated by awater jacket, it was not possible to switch it off while a test wasbeing made. By taking frequent readings it became clear that there is aninitial stage in drying in the rotary drier in which very rapid moistureloss takes place, from percent on entry, down to 70 75 percent in littlemore than an hour. It was thought probable that this represented surfacemoisture, easily lost. After this, there came a period in which aconsistent 2% 3 percent an hour was lost, and this continued until themoisture content was 35 40 percent. This was thought to represent waterwhich was less readily available, possibly because drying might betaking place only at the cut ends. At this stage there appeared adramatic and sudden increase in the rate of drying, which returned tothe initial rate of nearly percent in an hour. This latter increase wasunexpected, surprising and could not be predicated from conventionaldrying rate theory.

A study of how a solid dries may be based on the effect of the externalconditions of temperature, humidity, air flow, etc., on the drying rateof the solid or on the internal mechanism of liquid flow.

Internal liquid flow may occur by several mechanisms, depending on thestructure of the solid. The possible mechanisms are as follows:

1. Liquid Diffusion in continuous homogeneous solids.

2. Vapor Diffusion in any solid where heating takes place at one surfaceand drying at the other and where liquid is isolated between granules ofsolid.

3. Pressure Gradients Due to Shrinkage in solids in which shrinkageoccurs.

4. Capillary Flow in granular and porous solids.

5. Electroosmosis.

6. Gravity.

In general, one mechanism predominates at a given time in a solid duringdrying, and it is not uncommon to find different times during the dryingcycle.

Considering the morphology of vanilla beans and the fact that both theinternal and external structure of the bean pieces were exposed to thedrying medium during the observation of the unusual drying rate, itseems unlikely that the drying mechanism thereof is completely divorcedfrom chemical, biological, or biochemical phenomena, not presently fullyunderstood. At least it is impossible to formulate with certainty areasonable theory which would adequately and completely explain the rateof drying of vanilla beans based solely on the six internal mechanismsof liquid flow. However, interpretation of portions A and B (FIG. 2) ofthe drying cycle can be made in light of present understanding ofdrying.

The high rate of moisture loss observed the first hour of drying,portion A, may be explained as resulting from the evaporation of surfacewater. Most solids do experience a high constant rate of moisture lossat the beginning of the drying cycle and so the observed phenomenaduring portion A of drying process in the present instance is not at allunusual.

The succeeding hours, during which a slow constant rate of drying wasobserved, portion B, are probably due to moisture loss by liquiddiffusion. This mechanism appears to be the most likely becauseapproximately 80 per cent of the vanilla bean is a homogeneous solidwhich is a common medium for liquid diffusion. Also, most of themoisture which may be lost from the central portion of the bean(containing seeds and placental tissue) will enter the surroundinghomogeneous portion (ovary wall) and so, too, be subject to the laws ofliquid diffusion.

However, most solids experience a decrease in drying rate duringcomparable portions (i.e. to portion B) of their drying cycle.Therefore, an explanation of the observed constant drying rate of thevanilla bean must lie somewhere outside the realm of the internalmechanisms of liquid flow and include chemical, biological andbiochemical factors presently not fully understood.

The high rate of drying which occurred at the end of the cycle (portionC) when conducted in an ADT drier may possibly be partially explained bytwo mechanisms. One possibility is that liquid is forced to the surfaceby a pressure gradient that results from shrinkage of the outer layers.The second possibility is that during drying the differences in moisturecontent throughout the volume of the bean causes tiny cracks in the beanwhich exposes relatively large pockets of moisture to the drying medium.If the vanilla bean possessed the drying characteristics of most solids,it would complete its drying cycle at a steadily decreasing rate.Therefore here, as concluded hereinbefore, it is necessary to concludethat a true explanation of the observed high drying rate during portionC requires the consideration of other presently difiicult to assessfactors besides liquid flow theory.

Since the drying rate of vanilla beans is unique in comparison to thatof most other solids, complete and accurate theoretical interpretationis defied.

In addition to the difficulty in terminating the drying before the beanshad become overdried, it appeared that other constituents besides waterwere being lost, leading to unfavorable, lower chemical constants in thedried bean product.

Accordingly, it has now been discovered that if, upon approach of theonset of the latter increased drying rate, the bean pieces are removedfrom the ADT drier and dried in circulated air at ambient temperatureand humidity, a drying rate C of about 1 1.5 percent moisture by weightcan be established and maintained until the moisture content has beenreduced to the desired 20 25 percent by weight. The l 1.5 percentmoisture removal per hour eliminates overdrying as a processing problem.Furthermore, as the following Table l indicates, the constants obtainedwhen processing vanilla beans according to the present invention, showsubstantial improvement over comparable results from old conventionalprocesses.

TABLE 1 Analytical Constants on:

Uganda Grown Beans Madagascar Grown Beans New Conventionallyconventionally In the New Process example of Table l, the cured, partlydried bean pieces were removed from the rotary drier when their moisturecontent had been reduced to 35 40 percent by weight. These bean pieceswere spread about 4 inches deep in a conditioner comprising a perforatedtray through which air at room temperature and humidity were blown by afan. The tray perforations accounted for about 25 percent of the area ofthe tray bottom and consisted of a plurality of seven thirtyseconds inchdiameter holes. The fan moved about 3,000 CFM input air through the trayat room temperature and percentage humidity. Room temperature wasapproximately 86 F.; ambient air humidity was about 10 percent to 60percent. It was found that to facilitate the taking of periodic beanpieces percentage moisture content data and obtaining results which werestill pertinent, when the bean pieces percentage moisture content wasnearing 20 25 percent, it was easy to turn off the conditioner fan untilthe test results were known, then turn it back on if need for furtherdrying were indicated by the test results. This stopping and restartingof the conditioner appeared to cause no deleterious efiects.

When the bean pieces had been dried to 20 25 percent moisture content byweight, they were removed from the conditioner and packed in sealed cansfor shipment to a subsequent vanilla extraction process where the dataof Table I was obtained.

It should be evident from the foregoing discussion of details of thepresent invention that the term bean has sometimes been applied todesignate an approximately one-half inch long cut piece of bean. Theintention is believed to be clear from the context in each instance.

By use of the term cutting" to describe the action taken upon the greenbeans to cause them to become bean pieces no particular active mechanismis intended, the action words severing, slicing or chopping" would serveequally well to describe the active mechanism. Generally, the cutsproceed transversely of the long axes of the beans, although since noextra care is taken to maintain the beans exactly transverse to thecutter, some are cut on the bias into diamond shaped pieces withoutdeleterious effect.

It should now be apparent that the vanilla bean drying and curing asdescribed hereinabove possesses each of the attributes set forth in thespecification under the heading Background and Summary of the Inventionhereinbefore, Because the vanilla bean drying and curing of theinvention can be modified to some extent without departing from theprinciples of the invention as they have been outlined and explained inthis specification, the present invention should be understood asencompassing all such modifications as are within the spirit and scopeof the following claims.

What is claimed is:

l. A process for drying and curing green vanilla beans com prising:

chopping the beans into pieces each about one-half inch long;

curing the bean pieces within an enclosed space at about 140 F. forabout 70 78 hours; drying the cured bean pieces with heated, forced airat about 140 F. until the moisture content thereof is about 35 40percent by weight;

further drying said bean pieces in air at about room temperature andambient percentage humidity at a rate which lowers the moisture contentof said bean pieces about 1 l.5 weight percent per hour until themoisture content thereof is about percent by weight and said bean pieceshave a vanillin content of about 0.40 g/dl.

2. The process of claim 1 wherein step of curing said bean piecesincludes: depositing the bean pieces in perforated trays; stacking saidtrays within a curing tank; catching liquid exudate from the beampieces; and returning the exudate to the bean pieces.

3 The process of claim 1 wherein the further drying step includes:loading the bean pieces into perforated trays and blowing ambient airthrough said bean pieces and perforated trays.

4. The process of claim 3 wherein the substep of loading the bean piecesinto perforated trays includes leveling off the bean pieces to a depthof about four inches in the trays.

5. A process for drying and curing green vanilla beans comprising:

cutting the beans into short pieces having sufficient length of aboutone-half inch, as to be easily recognizable as vanilla bean pieces andbeing sufficiently short that a substantial part of the exterior of thebean pieces consists of exposed seeds, placental tissue and ovary wall;

curing said bean pieces by enclosing the bean pieces and maintainingthem at about F. for about 70 78 hours;

drying the cured bean pieces in air at elevated temperature until theonset of a drying rate that is substantially increased from about 2.5 3percent per hour to about 15 percent per hour;

further drying said cured bean pieces in room temperature air at ambienthumidity at a rate which lowers the moisture content of said bean piecesabout 1 1.5 weight percent per hour to a moisture content of 20 25percent moisture by weight and said bean pieces have a vanillin contentof about 0.40 g/dl.

6. The process of claim 5 including the further step of packing thedried, cured bean pieces in containers and sealing said containers.

2. The process of claim 1 wherein step of curing said bean piecesincludes: depositing the bean pieces in perforated trays; stacking saidTrays within a curing tank; catching liquid exudate from the beampieces; and returning the exudate to the bean pieces.
 3. The process ofclaim 1 wherein the further drying step includes: loading the beanpieces into perforated trays and blowing ambient air through said beanpieces and perforated trays.
 4. The process of claim 3 wherein thesubstep of loading the bean pieces into perforated trays includesleveling off the bean pieces to a depth of about four inches in thetrays.
 5. A process for drying and curing green vanilla beanscomprising: cutting the beans into short pieces having sufficient lengthof about one-half inch, as to be easily recognizable as vanilla beanpieces and being sufficiently short that a substantial part of theexterior of the bean pieces consists of exposed seeds, placental tissueand ovary wall; curing said bean pieces by enclosing the bean pieces andmaintaining them at about 140* F. for about 70 - 78 hours; drying thecured bean pieces in air at elevated temperature until the onset of adrying rate that is substantially increased from about 2.5 - 3 percentper hour to about 15 percent per hour; further drying said cured beanpieces in room temperature air at ambient humidity at a rate whichlowers the moisture content of said bean pieces about 1 - 1.5 weightpercent per hour to a moisture content of 20 - 25 percent moisture byweight and said bean pieces have a vanillin content of about 0.40 g/dl.6. The process of claim 5 including the further step of packing thedried, cured bean pieces in containers and sealing said containers.